1. Field of the Disclosure
The present invention relates in general to a mask structure that enables patterning small features on a workpiece using ions and, in particular, to a system, method and apparatus for a mask structure for ion implant magnetic patterning of magnetic media disks for disk drives.
2. Description of the Related Art
Patterning is part of the fabrication process used to create small features to build devices that process and store information. Ion bombardment or ion implantations are methods that are used for patterning. Ions are directed to impinge upon a sample thru a mask that has openings which can be used to pattern a sample. The ions locally change the properties of regions where they pass through or are stopped. The patterning can be in the form of changes to the local physical properties of the sample including microstructural, magnetic or electrical properties.
Ion implant tools are capable of generating the doses of ions that are needed to adequately change physical properties. There are a number of different kinds of implanting tools including plasma and ion beam implanters. High doses of ions are provided by these tools. However, it is necessary to develop new mask structures to enable the use of higher ion doses since masks that are exposed to an environment of high doses of ions or ions with higher masses can be partially susceptible to unwanted damage of the mask material. The damage can be in the form of thinning of the mask. If the mask is too thin, it can no longer perform its function of adequately stopping ions from entering the materials below the mask.
One cause of mask thinning is sputter etching of the mask material during the course of the implantation process. As the dose of implanting ions is increased, the amount of thinning correspondingly increases, to the point where conventional mask structures for ion implantation are not adequately robust against ion-induced erosion unless they are thick.
Unfortunately, the use of thick mask layers poses a number of challenges. As the size of the features to be patterned is made more narrow, the mask correspondingly has to be narrower. Relatively narrow and tall mask structures are mechanically weaker and prone to topple, creating defects in the patterned workpiece. Thicker masks also are less favored for manufacturing reasons. Mask structures are often deposited by vacuum deposition techniques and it can take more time to deposit a thicker mask, which adds undesired manufacturing cost. Thus, improvements in masks for ion implant magnetic patterning of workpieces continue to be of interest.
One method of reducing the sputter-induced erosion of the mask material is to make the mask out of a material having a lower tendency to be sputter-etched by the implanting ions. Sputter-etching means that the incident ions collide with the ions of the mask material and by transfer of energy and momentum cause the mask atom to be ejected from the mask. Repetition of the ejection of mask ions leads to sputter erosion or thinning of the mask material.
An example of a material that can be formed into a mask with a lower sputter rate is to fabricate the mask of a material that includes carbon. Carbon can be fabricated to have very low sputter erosion rates compared to many other materials. However, if used on its own as a mask material, carbon must be relatively thick to adequately stop the ions before they reach the layer to be patterned on the workpiece. It is desirable to make the mask thin. A way to make a thinner mask that initially stops the ions is to make the mask out of a material with good ion stopping power. However, many materials with good stopping power are very susceptible to high rates of sputter erosion. So again, a large thickness of the high stopping power material would be required to adequately stop the ions. What is needed is a mask structure that adequately stops ions, is subject to relatively small rates of erosion, does not need to be excessively thick, and can be fabricated readily for manufacturing.